1. Field of the Invention
This invention generally relates to an internal transmission hub assembly. More specifically, the present invention relates to an internal transmission hub assembly that includes a shift control sleeve (a pawl control member).
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle internal transmission hub assembly.
The internal transmission hub assembly is typically a rear wheel hub that includes an internal gearing mechanism that includes elements that can be shifted to provide a plurality of power transmission paths (gear ratios) for a cyclist.
With such an internal transmission hub assembly, a cyclist changes pedaling speeds by manipulating a conventional lever actuating shifting mechanism installed on or adjacent to the handlebars of the bicycle. Movement of the lever actuating shifting mechanism is transmitted to the internal transmission hub assembly by a Bowden-type cable that is operably connected to a shift mechanism within the internal transmission hub assembly. Changes in the position of the lever actuating shifting mechanism cause movement of various elements of the shift mechanism within the internal transmission hub assembly that ultimately determine the selection of a power transmission path (gear ratio).
The shift mechanism of the internal transmission hub assembly typically includes a shifting key guide, shift control sleeve (a pawl control member) and a sleeve guide. The shift control sleeve is pivoted about a stationary hub axle within the internal transmission hub assembly by the various elements of the shift mechanism of the internal transmission hub assembly.
The shift control sleeve (pawl control member) typically includes a base sleeve and one or more arcuately shaped control sleeves. The base sleeve typically extends in an axial direction along side a stationary hub axle with a first end and a second end. The first end of the base sleeve typically extends through an opening in the shifting key guide. Typically, no mechanical fastening is provided between the first end of the base sleeve and the shifting key guide. Specifically, the first end of the base sleeve extends through the opening in the shifting key guide. Consequently, the base sleeve is moved is a circumferential direction about the stationary hub axle by rotational movement of the shifting key guide. The control sleeves of the shift control sleeve (the pawl control member) are configured to engage and dis-engage pawls that selectively engage sun gears within the internal transmission hub assembly. The pawls act as one-way clutches to selectively stop rotation of the sun gears in one direction.
Typically, the second end of the base sleeve of the shift control sleeve (pawl control member) is confined in a recess formed in a sleeve guide that is also rotatably installed on the stationary hub axle of the internal transmission hub assembly. Typically, no mechanical fastening is provided between the second end of the base sleeve and the sleeve guide. Hence, the base sleeve of the pawl control member, the sleeve guide and the shift key guide move about the stationary hub axle as a single unit.
A problem with the base sleeve of the pawl control member, the sleeve guide and the shift key guide is that there can be minute amounts of play or slight relative movement between these elements. As with any mechanical device, play or slight relative movement between mechanically connected elements is undesirable. Over time, a loose or sloppy feel can be notice by a cyclist when shifting between power transmission path.
In one internal transmission hub assembly design disclosed in EP Patent Application Number 1,323,627, the second end of the base sleeve of the pawl control member is caulked or crimped within the recess of the sleeve guide, thereby initially eliminating play between the base sleeve and the sleeve guide. However, over time and extensive usage, play between the base sleeve and the sleeve guide may develop. Further the configuration disclosed in EP Patent Application Number 1,323,627 does not address the elimination of play between the shift key guide and the base sleeve of the pawl control member.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved internal transmission hub assembly that reduces or eliminates play between the base sleeve and the sleeve guide, and the shift key guide and the base sleeve of the shift control sleeve (the pawl control member). This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.